class WordItem {
  final int id; // Base index 0..999
  final int sessionNumber; // Dynamic randomized session number 0..999
  final String word;
  final String partOfSpeech;
  final double frequency;
  final String category;
  final String description;

  const WordItem({
    required this.id,
    this.sessionNumber = 0,
    required this.word,
    required this.partOfSpeech,
    required this.frequency,
    this.category = '',
    this.description = '',
  });

  WordItem copyWith({
    int? id,
    int? sessionNumber,
    String? word,
    String? partOfSpeech,
    double? frequency,
    String? category,
    String? description,
  }) {
    return WordItem(
      id: id ?? this.id,
      sessionNumber: sessionNumber ?? this.sessionNumber,
      word: word ?? this.word,
      partOfSpeech: partOfSpeech ?? this.partOfSpeech,
      frequency: frequency ?? this.frequency,
      category: category ?? this.category,
      description: description ?? this.description,
    );
  }

  String get formattedSessionNumber => sessionNumber.toString().padLeft(3, '0');
  String get formattedId => formattedSessionNumber;

  Map<String, dynamic> toMap() {
    return {
      'id': id,
      'sessionNumber': sessionNumber,
      'word': word,
      'partOfSpeech': partOfSpeech,
      'frequency': frequency,
      'category': category,
      'description': description,
    };
  }

  factory WordItem.fromMap(Map<String, dynamic> map) {
    return WordItem(
      id: map['id'] as int,
      sessionNumber: map['sessionNumber'] as int? ?? (map['id'] as int),
      word: map['word'] as String,
      partOfSpeech: map['partOfSpeech'] as String,
      frequency: (map['frequency'] as num).toDouble(),
      category: map['category'] as String? ?? '',
      description: map['description'] as String? ?? '',
    );
  }

  @override
  String toString() => '#$formattedSessionNumber: $word ($partOfSpeech)';
}